Method of making illuminated panel

ABSTRACT

An electroluminescent panel having a shell formed of lighttransmitting material and having an indicia bearing face to be illuminated. An electroluminescent member is positioned adjacent the ace within the shell which is filled with potting compound to a level encapsulating the member. The shell can be formed with an open-ended wall extending inwardly from the indicia bearing face to provide a socket for a control member.

United States Patent Coolbaugh et al. June 13, 1972 [54] METHOD OF MAKING ILLUMINATED [56] References Cited PANEL UNITED STATES PATENTS [72] inventors: Richard W. Coolbau gh, East Aurora; 2,787,652 4/ 1957 Kelsay ..264/272 Floyd W. Engels, G ld b h f my 3,461,551 8/1969 Kaup ....264/272 3,395,209 7/1968 Millard ....264/272 [731 Assgnw Cleveland, 01110 2,460,168 1/1949 Caserta ....264 154 22 i 3 s '0 2,958,762 1 1/1960 Cheney ..40/l30 M 3,133,221 5/1964 Knochel ..40/l30 M 21 App]. No.: 11,124

Primary Examiner-Robert F. White R la d 15- App Data Assistant Examiner-Richard H. Shear [62] Division Of Ser. N0. 694,967, Jan. 2, 1968, Pat. N6. may-Chm?! 35451110 57 ABSTRACT An electroluminescent panel having a shell formed of light- 52 us. c1 ..264/154, 40/130 M, 264/263, transmitting material and having an indicia healing face to be 264/272 illuminated. An electroluminescent member is positioned ad- 51 1 1m. c1 ..B28b 1/48, B296 6/00 3 the ace within the whim is fined with Pming [58] Field of Search 264/154 263 267 272 pound to a level encapsulating the member. The shell can be formed with an open-ended wall extending inwardly from the 1nd1c1a bearing face to provide a socket for a control member.

4 Claims, 7 Drawing figures 2/ g I: 7 9 I i\\\\ 1 I 6 =2 Q III/[VII qmqliiiiiiw.

INVENTOR.

PATENTEDJuu 1 3 m2 W m 09 N 5 w my in Mw A 5 METHOD OF MAKING ILLUMINATED PANEL This application is a division of pending application Ser. No. 694,967, filed Jan. 2, 1968, now U.S. Pat. No. 3,545,110

BACKGROUND OF THE INVENTION This invention relates generally to the illuminating art, and more particularly to the illumination of instrument and control panels and the like.

The illumination of instrument and control panels such as are found in automobiles and aircraft poses a number of problems. A common practice has been to direct one or more light sources onto the surface of the panel. However, such reflected light can cause considerable strain over a period of time. This is annoying, and can be quite dangerous when close attention must be paid to the panel as in the cockpit of an aircraft.

Various other arrangements have been proposed, including the utilization of special light sources. However, this can become quite complex and expensive. It has been proposed, for example, to provide a plastic panel having small incandescent lamps imbedded within the plastic, in alignment with the indicia on the panel. However, under severe stress and vibration such lamps tend to fail, because the filament is essentially a spring having a natural frequency and when the vibration frequency is such that the filament resonates it can vibrate to destruction. Once an individual lamp is destroyed, the problem of replacing it is complex and often requires replacing the entire panel section.

Electroluminescent sources of light are known, and are commercially available. They comprise metal having a ceramic coating containing phosphors which glow under conditions of electrical excitation. However, such electroluminescent members, being of capacitive-resistive nature, pose an electrical hazard. For this and other reasons such light sources have not heretofore been considered particularly suitable for panel illumination.

SUMMARY OF THE INVENTION This invention provides a means for the effective utilization of such electroluminescent sources of light for panel illumination. In carrying out the method of this invention, the electroluminescent members are so incorporated in the panel structure as to become an integral part thereof, in a manner insuring the complete insulating of the electroluminescent member from surrounding electrically conductive materials.

The primary object of this invention is to provide a panel containing an electroluminescent source of illumination wherein the source is incorporated in the panel in an electrically insulated manner causing it to become an integral part of the panel structure,

Another object of this invention is to provide a method for accomplishing the foregoing in a relatively simple and inexpensive manner.

Still another object of this invention is to provide an electroluminescent panel of outstanding reliability and performance.

The foregoing and other objects, advantages and characterizing features of this invention will become apparent from the ensuing detailed description, reference being made to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is a front elevational view of an illuminated instrument and control panel constructed in accordance with this invention, as it would appear in use;

FIG. 2 is a top plan view of the panel shell after forming thereof;

FIG. 3 is a cross sectional view thereof taken about on line 3-3 of Fig. 2;

FIG. 4 is a view of the panel during an intermediate stage of construction;

FIG. 5 is a fragmentary, detail view in cross section, illustrating the attachment of a control member to the panel;

FIG. 6 is a fragmentary, cross sectional view of a modified panel construction; and

FIG. 7 is a fragmentary perspective view of an electroluminescent member and its leads.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring now in detail to the accompanying drawing, there is shown an illuminated panel of our invention, generally designated 1, having indicia 2 thereon and also having control switches 3 and push buttons 4 projecting therefrom or arranged therein. It will by understood, however, that the articular panel shown in FIG. 1 is only illustrative of the many varied arrangements which can be provided in the panel of this invention.

The panel structure includes a shell of plastic material having a face portion 5 interrupted at various locations by welldefining sleeves 6 projecting rearwardly from face 5 which extends across the panel and is bounded by a peripheral skirt 7. In the illustrated embodiment, the shell is formed of a light transmitting, synthetic plastic material, and the indicia 2 are provided by silk screening or otherwise depositing an opaque layer 9 over face 5 in a manner outlining the indicia 2. However, other indicia forming techniques can be utilized.

An electro-luminescent member generally designated 10 having energizing leads 11 is positioned within the shell, behind face 5 and behind the indicia 2 intended to be illuminated by that particular member. In FIGS. 4 and 5, member 10 is annular and encircles a well 6, but the member 10 can be formed in any desired shape. Member 10 is incapsulated in the shell by potting compound 12 which fills the shell defined by face 5 and skirt 7 surrounding the wells 6. A switch 13 actuated by the member 3 can have a face ring 14 clamped against the outer face of the panel by a nut 15 engaging the rear face thereof.

Referring now to FIGS. 2, 3, and 4, the panel 1 is manufactured as follows. A master die plate 16 is made in any suitable manner, having a peripheral dimension defining the skirt 7 and having a face defining the panel face 5. Openings are provided through plate 16, dimensioned to provide the well defining skirts 6. The shell is formed by taking a sheet of suitable thermoplastic material, such as for example a cellulose acetate, styrene or poly vinyl resin. The plastic sheet is heated to a state of plasticity and vacuum formed over plate 16 to the configuration shown in FIG. 3. Such vacuum forming will be readily understood by those skilled in that art, but it will be noted that in such vacuum forming the well defining sleeves 6 terminate at their inner ends in a wall 17 which is parallel to face 5 but spaced beyond the peripheral flange 8, for reasons which will become apparent.

The shell is removed from plate 16, and inverted on a plate, table or other supporting surface 18 of magnetic material. The support member 18 can be permanently magnetized, or can be arranged for intermitent electromagnetic energization.

The electroluminescent members 10 can be of conventional, commercially available form. These are available in various plate forms and can be constructed in other configurations, Members 10 themselves comprise no part of our invention, and being a commercially available product well understood by those skilled in the art a detailed description is believed to be unnecessary. Suffice it to say that an electrically conductive plate 18 provides one electrode of the luminescent cell. A layer of electroluminescent phosphor material 19 is positioned between the electrode plate 18 and a second electrode 20. The plate 20 can comprise a thin layer of electrically conducting material evaporated or otherwise superposed onto the phosphor layer 19, which latter is suspended in a dielectric plastic.

The conducting layers 18, 20 are connected in an alternating current circuit including the leads 11, causing the phosphor layer 19 to emit light which is transmitted through the thin, highly translucent layer 20. The layer 18 can be light reflecting toward the layer 20.

In carrying out the method of our invention, the various luminescent cells 10 are positioned within the shell against the inner side of face 5, behind the indicia to be illuminated by that cell. In FIG. 4, two cells of annular shape are shown, encircling the sleeves 6 for illuminating indicia 2 adjacent those wells. It will be appreciated that cells 10 could comprise a single member having cutout portions to receive the various well defining sleeves 6, or two or more cells having whatever shape is necessary to overlie the indicia 2.

After the various cells 10 have been positioned within the panel shell, the latter is filled with a conventional electrically insulating potting compound 21 to a level above the cells 10 and preferably approaching or at the level of the peripheral flange 8. By filling the interior of the shell with potting compound 21, cells 10 and their connections to the leads 11 are completely incapsulated and insulated, and the connection between cells 10 and their leads 11 is reinforced by the surrounding potting compound.

As seen in FIG. 4, the closed inner ends 17 of the wells are spaced above the level of flange 8. After the shell has been filled with compound 21, the inner ends of the wells are severed, preferably in or closely adjacent the outer surface of the potting compound 21, whereupon the sleeves 6 are coextensive in length with the thickness of the potting compound, as clearly shown in FIG. 5, and flange 8 is trimmed away. If the indicia 2 have not already been provided on face of the panel, they are now provided as by silk screening onto the face 5 an opaque layer 9 of a material containing a solvent for the plastic used in making the shell. This causes the ink of layer 9 to penetrate and bond with face 5. In applying the opaque layer, the indicia 2 are omitted, whereby they are formed by the surrounding layer 9, in a manner well understood by those versed in this art. Obviously, the indicia can be provided in other ways.

Then, the various switches, indicator lights or whatever is to be mounted in the panel, are so mounted, and the panel is ready for use.

It is a particular feature of our invention that the luminescent cells are properly and effectively positioned behind the face 5. Even with a cell which does not encircle a well sleeve 6, but instead is positioned between such sleeves, in spaced relation thereto, accurate positioning is insured by the utilization of a magnetic support 18. Such cells include a magnetic material, whereby they are attracted to the support 18. This means that the cell remains in the position in which it is placed, although it can be slid back and forth on the inner surface of face 5, to achieve the desired positioning. Also, it means that the cell 10 can have its surface 20 tightly engaged against the inner surface of face 5, in snug fitting engagement therewith, This is important where maximum legibility and angle of vision are required, because it precludes the entry of potting compound between cell 10 and face 5. Such cells are relatively light weight, and if it were not for the force of magnetic attraction holding them tightly against the face 5 of the panel shell, they could be dislodged from the surface as the shell is filled with potting compound and this can interfere with the total Iegibility of the illuminated panel.

Also of significance is the fact that sleeves 6 not only provide a well for receiving control members or indicators, but also function to insulate the adjacent cell 10 from whatever member is positioned within the wall. In other words, in a panel as shown in FIGS. 4 and 5 it is clear that the cells 10 are completely incapsulated within the panel, bearing against the sleeve 6 and the face 5 which insulate the corresponding surfaces of the cell, and the remainder of the cell being insulated by the potting compound 21.

Further, the potting compound fills the shell, causing the cells 10 to be united with the shell and the potting composition to provide a monolithic panel body of substantial structural integrity.

Where desired, the parcel shell can be formed to provide thin web sections 35 extending from and between illuminated sections as defined by inner skirt portions 7 as shown at the right-hand side of FIG. 4. Webs 35 can provide inwardly offset panel sections in areas where the thick, encapsulated section is not desired.

Accordingly, it is seen that our invention fully accomplishes its intended objects. While only two embodiments have been described in detail, that has been done by way of illustration, it being understood that our invention is not necessarily limited thereto.

Sometimes it is desired to illuminate the socket through the wall 6, adjacent the face 5. This can be accomplished with our invention by using an electroluminescent member 10' which is of the same construction as member 10 except that it includes a portion 23 which is formed out of the plane of the portion 24 which is parallel to face 5 and which illuminates the indicia 2. The member 10 is positioned around or adjacent the well to be illuminated, and because it faces the juncture between walls 5 and 6 it will illuminate the area 25 of the shell surrounding the outer end of the wall, as shown in FIG. 1, This will assist the observer in locating the push bottom 4 or other actuating device positioned within the well. The juncture between face 5 and wall 6, comprising the area 25, can be curved in concentric relation to the light cell portion 23.

In addition to legends, numerals and other such indicia, the illuminated panel of our invention can include an illuminated border or outline around either the entire panel or selected portions thereof. To this end, face 5 is formed with a border or frame defining groove 26 which can extend completely around the panel, for example spaced inwardly a fraction of an inch around the opaque face of the panel shown in FIG. 1, or which can outline selected portions thereof.

To illuminate groove 26, a member 10 or 10' is positioned immediately behind groove 26, adjacent indicia 2. By silk screening or otherwise opaquing face 5 except in groove 26 and at indicia 2, the member 10, 10' will illuminate the outlining groove 26 as well as the indicia 2. The outer edge portion of face 5, to the left of groove 26 as viewed in FIG. 6, can be covered with the opaque layer 9, leaving only groove 26, indicia 2 and areas 25 uncovered and light transmitting. Also, by appropriately shaping groove 26 and the marginal portions of face 5, a variety of asthetically pleasing, sculptured effects can be obtained.

It will be appreciated that where the electroluminescent member l0, 10 is adjacent but is spaced from the face 5, as in FIG. 6, it must nonetheless be positioned close thereto, and must be light coupled therewith. To this end, a transparent potting compound 21, such as a suitably transparent epoxy resin is used to fill the shell after the member 10 has been positioned therein. Prior to filling the shell with potting compound the member 10, 10' can be magnetically held against face 5 and groove 26. However, where the member 10, 10' is large enough in area to contact groove 26 at spaced points, it will be supported by the groove at an elevation above face 5 and will be adjacent but not necessarily in actual contact with face 5 other than at groove 26.

As previously noted, where maximum legibility and angle of vision are desired, member 10, 10' should be positioned tightly against face 5 to avoid the losses associated with spacing them apart. Where groove 26 is not provided, portion 24 of member 10' can be in contact with face 5 and portion 23 in contact with area 25.

We have found that potting compound 21 tends to slope somewhat, due to capillary attraction, whereby it will be spaced further from face 5 where it is in contact with the side wall surfaces 6 and 7. Often it is desirable to have a back face which is parallel with the front face, for positioning against a panel. To this end, after the potting compound has set, the rear face is cut to a level representing the desired thickness of the panel. This can be accomplished by means of a router, care being taken to rout around the leads 1 l.

Preferably, the electrical leads are brought together and protected by an insulating, reinforcing sleeve 30 which latter is surrounded by potting compound 21. Sleeve 30 preferably has a lateral flange 31 providing a base which seats upon the member 10 or 10. Leads 11 extend through sleeve 30 and outwardly through a side wall opening 32 therein adjacent base flange 31 which is cut away at 33 in alignment with opening 32. This permits leads 11 to extend through sleeve 30 to member or 10' and then outwardly across the member 10, 10. One lead is secured to a clip 34 which is insulated from plate 18 and dielectric layer 19 but extendsaround member 10, 10 to the opposite plate 20 in electrical contact therewith. The other lead 11 is secured to plate 18 in electrical contact therewith, as by a silver conductive epoxy adhesive, the terminal end of that lead also being held against plate 10 18 base flange 31 which is adhesively bonded to plate 18.

When using reinforcing sleeve 30 the potting compound 21 tends to fill the interior of the sleeve through opening 32 by capillary action. The upper end of the sleeve opening is filled with a resiliently yieldable, insulating material, such as an RTV silicone resin, whereby the leads 11 are yieldably positioned within member 30.

Reinforcing member 30 protects leads 11 both during the potting of the panel shell and after, providing a convenient means of handling the leads during the potting operation. The back face of the panel is routed or otherwise cut to a predetermined thickness, around sleeve 30 which then projects behind the illuminated panel for insertion through an opening in the panel structure adapted to receive the same.

We claim:

1. The method of making an illuminated panel having a socket opening therein which comprises forming a panel face of light-transmitting electrically insulating material having a well projecting from one side thereof, placing an electroluminescent member adjacent said one side of said face with the inner end of said well extending beyond said member, encapsulating the exposed portions of said member with an electrically insulating potting compound which extends above said member but below said well, and severing the inner end of said well closely adjacent the outer surface of said potting compound to provide an insulated socket substantially co-extensive in length with the thickness of said potting compound.

2. The method of claim 1 wherein said electroluminescent member is magnetic, and wherein said member is held in position adjacent one side of said face by magnetic means on the opposite side thereof while encapsulating said member with potting compound.

3. The method of claim 1, together with the step of providing indicia on said face.

4. The method of claim 3, wherein said indicia is provided by rendering said face opaque around said indicia. 

1. The method of making an illuminated panel having a socket opening therein which comprises forming a panel face of lighttransmitting electrically insulating material having a well projecting from one side thereof, placing an electroluminescent member adjacent said one side of said face with the inner end of said well extending beyond said member, encapsulating the exposed portions of said member with an electrically insulating potting compound which extends above said member but below said well, and severing the inner end of said well closely adjacent the outer surface of said potting compound to provide an insulated socket substantially co-extensive in length with the thickness of said potting compound.
 2. The method of claim 1 wherein said electroluminescent member is magnetic, and wherein said member is held in position adjacent one side of said face by magnetic means on the opposite side thereof while encapsulating said member with potting compound.
 3. The method of claim 1, together with the step of providing indicia on said face.
 4. The method of cLaim 3, wherein said indicia is provided by rendering said face opaque around said indicia. 